Periodontal disease (PD) is a common oral condition and a leading cause of tooth loss. It is a polymicrobial infection characterized by gingival inflammation stimulated by bacterial colonization resulting in soft tissue destruction and alveolar bone resorption. Interestingly, herpes simplex virus 1 (HSV-1) is frequently associated with periodontal lesions. It is thought to be a co-factor that may increase an individual's susceptibiliy to PD by damaging gingival tissue and sustaining local inflammation. Saliva is known to contain antiviral and antimicrobial agents, including components that act on the HSV virion to prevent infection. For the first time, we observed that saliva from some individuals but not others contains a component that increases the susceptibility of gingival fibroblasts to HSV-1 infection. This effect can favor viral spread and broaden HSV tropism to cells that are exposed in periodontal lesions. This unexpected observation of a novel salivary effect prompted us to explore it further in this application. Thus, the goals of this study are to identify this factor ad its effects in order to understand how HSV-1 efficiently spreads in the oral cavity and how it may exacerbate the progression of PD. Two aims are proposed to achieve these objectives: In aim 1, we will identify the salivary protein that increases cell susceptibility to infection. We will combine biochemical fractionation and functional infection assays to purify the active agent. Identification will be performed by mass spectrometry, 2D-gel electrophoresis and biochemical assays on active purified fractions. Novel preliminary data showing that jacalin depletes saliva of its activity suggest a role for carbohydrates on glycoproteins, mucins and/or IgA. Thus we will examine the role of carbohydrates and use this lectin to improve purification. We will also determine if prior infection by HSV relates to the stimulatory effect of saliva by investigating th role of secretory IgA. In aim 2, we will first define how gene expression is affected by exposure to saliva in various cells of oral origin. We have enlisted experts to aid in analyzing microarray data. We will also use model cell lines to define how saliva stimulates HSV-1 entry at the level of receptor interaction, entry pathways and membrane fusion. Finally, to relate this effect to in vivo infection, we will survey primary human oral cells and HSV clinical isolates. We have access to a variety of such cells and viruses by virtue of collaborators here at PENN. The identification of a salivary agent that acts on oral cells to favor HSV-1 infection sets a new precedent. It will open new areas of investigation and facilitate studies of the role of HSV-1 in the progression of PD. Since the activity is not present in the saliva from all individuals, we wil be able to further test it as a biomarker for susceptibility to oral herpes and possibly PD. This agent will provide an accessible target for therapeutic interventions to prevent HSV spread in the oral cavity and limit its potential aggravating activity in periodontitis.